Fireplace heated grate

Abstract

A hollow heated grate for a fireplace is provided with an electric motor and a blower inside of the heated fireplace enclosure for circulating cool air from the area to be heated through the hollow grate and returning the heated air to the area to be heated. The electric motor and blower are physically enclosed in a metal plenum box. To avoid overheating the electric motor windings, cool air is circulated over the motor windings when the electric motor is running and cool air is also circulated over the electric motor windings when the electric motor is not running by novel diversionary air vent means including sensing means for opening a movable closure adjacent the diversionary air vent when the electric motor and blower are not circulating cool air.

We claim: 
     
       1. A plenum for cooling an electric motor in a fireplace enclosure environment, comprising: a box shaped plenum adapted to be placed in a heated fireplace,   an electric motor mounted in said plenum,   a blower connected to said electric motor in said plenum,   an inlet to said blower inside said plenum,   an outlet port in said plenum,   an outlet from said blower connected to said outlet port in said plenum,   a cool air inlet port in said plenum,   a diversionary air vent in said plenum located at an elevation above said cool air inlet port,   said diversionary vent comprising a normally open movable closure,   said movable closure adapted to be opened when said electric motor and said blower are not circulating cool air through said plenum, and   means for closing said movable closure when said electric motor and said blower are circulating cool air through said plenum, whereby cool air is circulated from said cool air inlet port through said diversionary air vent when said plenum is hot, thus creating convection cooling of said electric motor when said electric motor is not running.   
     
     
       2. A motor plenum as set forth in claim 1 wherein said means for closing said movable closure comprises an electric solenoid means. 
     
     
       3. A motor plenum as set forth in claim 1 wherein said means for closing said movable closure comprises spring closure means. 
     
     
       4. A motor plenum as set forth in claim 3 wherein said spring closure means further comprises a damper lever located in the outlet from said blower to said outlet port. 
     
     
       5. A motor plenum as set forth in claim 1 wherein said means for closing said movable closure further includes bi-metallic spring means biased to open said movable closure when the air in said plenum is hot. 
     
     
       6. A motor plenum as set forth in claim 1 wherein said means for closing said movable closure comprises a mechanical thermostat coupled to open said movable closure when the temperature in the said plenum rises above 140° degrees fahrenheit. 
     
     
       7. A motor plenum as set forth in claim 1 wherein said means for closing said movable closure comprises a temperature sensitive element which opens said movable closure indicating that the electric motor is not properly circulating air from said cool air inlet port in said plenum to cool said electric motor. 
     
     
       8. A motor plenum as set forth in claim 1 which further includes a baffle inside said plenum adjacent said cool air inlet port for directing the cool air from said inlet port over the windings of the electric motor before being directed to said diversionary air vent during convection cooling. 
     
     
       9. A motor plenum as set forth in claim 2 which further includes temperature sensitive switch means for energizing said electric motor and said electric solenoid means. 
     
     
       10. A motor plenum as set forth in claim 1 wherein said means for closing said movable closure comprises a baffle plate slidably mounted on the side of said plenum and adapted to be moved to cover said diversionary air vent when said electric motor is normally not energized to circulate cool air through said plenum. 
     
     
       11. A motor plenum as set forth in claim 10 wherein said slidable baffle plate is spring biased in engagement with the side of said plenum and provided with a lever for sliding said plate up and down. 
     
     
       12. A method of maintaining an electric motor in a fireplace plenum enclosure at a relatively low operational temperature, comprising: enclosing said electric motor in a metal plenum box,   providing a lower intake port in the side of said metal plenum,   providing an upper diversionary vent port on the same side of said metal plenum,   providing an outlet port on the side of said metal plenum,   providing an electric blower connected to said electric motor and having a blower inlet inside of said metal plenum and a blower outlet connected to said outlet port,   means for opening said diversionary vent when said electric motor is not running, and   closing said diversionary vent when said electric motor is running, and normally exhausting cool intake air from said lower intake port out through said diversionary vent when said electric motor is not running by convection heating the cool intake air with the heat of said metal plenum thereby providing convection cooling for said electric motor.